Re: [libgpiod][PATCH 18/22] bindings: python: tests: add missing type annotations

[Bartosz Golaszewski <brgl@xxxxxxxx>]

On Wed, Oct 9, 2024 at 6:41 PM Vincent Fazio <vfazio@xxxxxxxxx> wrote:
>
> On Tue, Oct 8, 2024 at 8:32 AM Bartosz Golaszewski <brgl@xxxxxxxx> wrote:
> >
> >
> > I admit I don't know any better but does it really make sense to do it
> > for individual test cases?
>
> Some projects type their tests while others don't make it a priority. The way I
> see it, the overhead is minimal when adding a new test so why not add it.
>
> One of the caveats is that mypy does not type check the bodies of functions
> that have untyped function definitions. So:
>
>   def _internal_fn(arg: str) -> str:
>     return arg
>
>   def test_fn():  # will not be type checked by default
>     _internal_fn(10)  # so this will not raise a type error
>
> It seems important to ensure the test cases are either abiding by the typed
> library interface or knowingly using invalid arguments to test "negative" cases
> (type errors which are suppressed in patch 19) for callers who do not leverage
> or ignore the library's type annotations.
>
> When fixing the type annotations for gpiod, I used the tests and examples as a
> reference for what the call interface is expected to support.
>
> For the situation above re untyped function definitions, mypy does have a knob
> that allows type checking the bodies of untyped functions. If we used that, it
> could be argued that the majority of this patch could be dropped.
>
> So, I guess some questions:
>
> Do you want the test suite type checked?
>

Yes, you've already done most of the work, so I'm all in favor of
keeping it. I see value in having everything typed and I don't expect
to be writing a lot of new tests so it won't involve much overhead.

> If not, a lot of the patches touching tests can be dropped
>
> If you do, to what degree? Do you want function bodies type checked?
>

I take it your changes already do it? Sure, let's keep it.

> For example, mypy identified the problems in patch 14 and 16. Even if untyped
> functions aren't checked, those problems would still have been flagged.
>
> If you think there's value in type checking functions, do you want to use
> explicitly typed function signatures or leverage `check_untyped_defs` [0] (this
> could be added to the mypy configuration in pyproject.toml).
>

Thanks,
Bart